[The dependence of rhythmic myocardial inotropism on the degree of stretching]. / Zavisimost' ritmoinotropii miokarda ot stepeni rastiazheniia.

The length-dependence of force-frequency relations in rat heart was studied in isometrically contracting papillary muscles. Negative force-frequency relations were observed for all lengths; the slope of the optimal length curve (Lopt) corresponding to peak contractile force during rhythmic pacing at 0.5 Hz, was greater than that for both 0.7 Lopt and 1.20 Lopt. The slope of static force-frequency curve was estimated at various muscle lengths in the range between 70 and 120% of Lopt. It was concluded that: 1) the heart muscle length corresponding to the maximal peak contractile force depends on stimulation frequency; 2) the slope of the force-frequency curve is maximal at the muscle length of 90 to 95% optimal length determined at basis stimulation frequency (0.5 Hz). The operating point for heart muscle in vivo is believed to be biased from the maximum of length-tension curve to its ascending part.

[Chronoinotropic reaction of the hypertrophied myocardium using an electromechanical coupling mathematical model]. / Issledovanie khornoinotropnoi reaktsii gipertrofirovannogo miokarda s pomoshch'iu matematicheskoi modeli élektromekhanicheskogo sopriazheniia.

Static and dynamic chrono-inotropic responses were recorded from both normal and hypertrophic rat auricular myocardium. The slope of the static force-frequency relation from hypertrophied heart was steeper than in the control hearts. The cellular mechanisms underlying changes in the force frequency response associated with hypertrophy of the heart were studied by means of a mathematical model of excitation-contraction coupling. The characteristic features of hypertrophied heart force-frequency relations are shown to be due to the enhanced volume of the intracellular Ca-stores in contrast to the total volume of the cardiomyocyte.

[Interaction between plasma lipoproteins and bilayer lipid membranes. The role of surface charge]. / Vzaimodeistvie lipoproteidov plazmy s bisloinymi lipidnymi membranami. Rol' poverkhnostnogo zariada.

Interactions of planar BLM with different thickness and surface charge were analysed theoretically. Drawing together of the membranes is accompanied with the appearance of intramembrane potential jumps which may cause destruction and breakdown of the membranes. The theory is extrapolated to the interaction between spherical lipoprotein particles and planar BLM. Experimentally calculated (by means of ESR) surface charges of lipoproteins of low density (LLD) (--0,3 . 10(-2) C/m2) and lipoproteins of high density (LHD) (--2 . 10(-2) C/m2) enabled calculation of the interaction energy between the particles and BLM as well as of the values of intramembrane potential jumps. The latter cause local reconstructions of the membranes in the contact region and fusion of the particles with them. The earlier obtained experimental data were proved by the finding that LHD adsorption as compared with LLD is impeded due to the existence of a high energetic barrier. These peculiarities of the particles manifested during their interactions with BLM seem to be one of the factors responsible for atherogenic function of LLD and antiatherogenic one of LHD.

[Membrane interaction with regard to redistribution of charged components]. / Issledovanie vzaimodeistviia membran s uchetom pereraspredeleniia zarazhennykh komponentov.

A system of two plane charged bilayers in electrolyte solution was considered with regard to possible redistribution of the charged lipids under the effect of the electric field. Force and energy conditioned by electric and van der Waals interaction were analysed. Two possible mechanisms of charge redistribution were proposed and analysed: the lateral one and by the "flip-flop" type. The results for these redistribution types were compared with those for fixed charge density. Relationships between inner field on the membrane surface potential differences resulting forces and energies and the distance between the membranes and the effect of charge redistribution were analysed. The redistribution of the surface charge was shown to weaken the pushing part of the membranes and to decrease the intermembrane field, which promotes the adhesion without damaging the membrane structure.

[Interaction of membranes with constant surface charge]. / Vzaimodeistvie membran, nesushchikh postoiannyi poverkhnosthyi zariad.

A system of two plane charged bilayers in electrolyte solution is considered. Equilibrium criteria of such system under the effect of van der Waals attractive forces and electrostatic repulsive force were obtained, as well as aggregation criteria (it is assumed that surface charge density on the membrane is constant). Relationships between the membrane inner field, surface potential differences, as well as resulting forces and energies and the distances between the membranes were analysed.